At present, LED products are applied to daily life in a great amount. Because of advantages of LEDs (light emitting diodes) such as stable performance, easy and inexpensive manufacture, and low power consumption, conventional halogen lamps are gradually replaced with LEDs. However, due to own characteristics of LED light sources, light emitted hereby have to be subjected to secondary optical processing; otherwise, application requirements inmost application situations will not be satisfied. For this reason, LED light sources have to be equipped with a lens, and a specially designed lens can enable light emitted by the LED light sources to achieve expected effects.
For practical applications, for example, a plurality of LED chips distributed in an array is usually used in a streetlight which utilizes LED chips as light sources, and a special lens is equipped for each LED chip or a common lens is equipped for the plurality of LED chips. However, a problem often occurs, viz. the assembly accuracy between the LED chips and the lens determines whether the practical illuminating effect of the streetlight is good or bad. In order to solve the above problem, several technical solutions are raised in the prior art, wherein according to a technical solution, an erection column is formed on the lens, a threaded hole is formed in the erection column, and the lens is fixed on a circuit board by screwing a bolt into the threaded hole. However, such a bolted connection mode cannot well assure the assembly accuracy between the lens and the LED chips. Another technical solution provides that an assembly hole is opened on the circuit board, while a locating pin is formed on the lens, said locating pin is inserted into the assembly hole, and a part of the locating pin, which is exposed through the circuit board, is melted at the other side of the circuit board and forms a fixing and holding part after cooling. However, the disadvantage of said technical solution lies in that a gap exists between the locating pin and a mounting plate, which might result in a relative displacement of the lens with respect to the LED chips, and then detrimentally influence the illuminating performance of the illuminating device.